1. Field of the Invention
The present invention relates to dictation systems and, more particularly, is directed toward a dictating apparatus for use in dictation systems using a telephone communication network to interconnect a plurality of dictating apparatuses at remote locations with a record/playback station at a central location.
2. Description of the Prior Art
Considerable effort has been made in the past to develop tone operated and voice actuated (VOX) apparatuses for remote dictating systems having a plurality of dictating units and a central record/playback station. In a tone operated apparatus, distinctive audio tones are transmitted through a pair of audio signal lines from a telephone to a record/playback system. These audio tones control operation of the record/playback system and the transmission of input and output audio signals. Generally, tone actuated apparatus utilize dual tone multiple frequency DTMF tones, the same tones that are used in telephone instruments. The DTMF keypad on a telephone instrument has twelve buttons or keys not all of which are used in tone operated record/playback systems. Most users are not able to depress the correct button without looking at the keypad. Therefore, such users must direct their attention to the keypad buttons rather than to the object which they may be studying while recording or playing back a previously recorded message. In addition, the operator must hold the handset in one hand and use the other hand to press the proper key on the keypad. A tone controlled dictation apparatus is shown in U.S. Pat. No. 3,691,300.
Dictation systems using voice actuated techniques were introduced in an attempt to overcome the disadvantages of making the operator look at the keys in the telephone keypad in order to operate the system. In the voice actuated technique, the presence of audio signals on the transmission wires are detected by detection circuits at the record/playback system. Tone control signals may be used in conjunction with voice actuated audio signal detection for controlling playback, rewind and forward functions. With this combination, the operator can record speech without having to be concerned about depressing the keys during dictation, but he must still use the keypad for generating control functions. A major disadvantage of the voice actuated system is its inability to work effectively over widely varying ambient room noise conditions and voice attenuation characteristics of the public telephone lines. In an environment with background noise, for example machines or people talking, the voice actuated circuit may interprete background noise as dictated audio signals and enter into a record mode. If the threshold sensitivity of the voice actuated circuit is increased to avoid false triggering on background noise, it is possible that low level dictation may not activate the circuit. This problem is compounded by the attenuation characteristics of telephone networks.